The relation between photocurrent and iron distribution in as-grown bulk InP is studied on the basis of a theoretical model that considers the electronic transitions involving and electronic levels. The photocurrent contrast is thus analysed in terms of fluctuations in and . When studying the homogeneity of Fe-doped semi-insulating InP wafers by means of scanning extrinsic photocurrent microscopy, it is seen that inhomogeneity is mainly controlled by fluctuations of the neutral iron concentration .